A gas turbine engine typically includes a fan section, a compressor section, a combustor section, and a turbine section. Air entering the compressor section is compressed and delivered into the combustion section where it is mixed with fuel and ignited to generate a high-speed exhaust gas flow. The high-speed exhaust gas flow expands through the turbine section to drive the compressor and the fan section.
The compressor section and/or the turbine section may include rotatable blades and stationary vanes. A blade outer air seal (BOAS) may be mounted within the engine casing, and positioned in close proximity to the outermost tips of the rotatable blades. Space between the BOAS and the blade tips may be maintained to avoid the blade tips rubbing against the BOAS due to the expansion of the blade relative to the BOAS. However, the efficiency of the gas turbine engine may be undesirably affected by having a large tip clearance between the blade tips and the BOAS, as the hot gas flow may leak through the space between the blade tip and the BOAS.